Age differences in the relationships between risk factors and loss of kidney function: a general population cohort study

Clinical Outcomes in Patients with CKD and Rapid or Non-rapid eGFR Decline: A Report from the DISCOVER CKD Retrospective Cohort

INTRODUCTION

This analysis examined the baseline characteristics and clinical outcomes of patients with chronic kidney disease (CKD) and rapid or non-rapid estimated glomerular filtration rate (eGFR) decline, using retrospective data from DISCOVER CKD (ClinicalTrials.gov, NCT04034992).

METHODS

Data (2008-2020) were extracted from UK Clinical Practice Research Datalink, US TriNetX, US Limited Claims and Electronic Health Record Dataset, and Japan Medical Data Vision. Patients with CKD (two consecutive eGFR measures < 75 mL/min/1.73 m2 recorded 90-730 days apart) were included. Rapid eGFR decline was defined as an annual decline of > 4 mL/min/1.73 m2 at 2 years post-index; non-rapid eGFR decline was defined as an annual decline of ≤ 4 mL/min/1.73 m2. Clinical outcomes assessed included all-cause mortality, kidney outcomes (composite risk of kidney failure [progression to CKD stage 5] or > 50% eGFR decline, and kidney failure alone), cardiovascular events-including major adverse cardiovascular events (MACE; non-fatal myocardial infarction/stroke and cardiovascular death)-and all-cause hospitalization.

RESULTS

Across databases, rapid eGFR decline occurred in 13.7% of 804,237 eligible patients. Mean annual eGFR decline ranged between - 6.21 and - 6.86 mL/min/1.73 m2 in patients with rapid eGFR decline versus between - 0.11 and - 0.77 mL/min/1.73 m2 in patients with non-rapid eGFR decline. Rapid eGFR decline was associated with increased comorbidity burden and medication prescriptions. Across databases, the composite risk of kidney failure or > 50% decline in eGFR was significantly greater in patients with rapid versus non-rapid eGFR decline (P < 0.01); all-cause mortality, kidney failure alone, MACE, and all-cause hospitalization each significantly increased in two databases (P < 0.01-0.05).

CONCLUSION

Understanding patient factors associated with rapid eGFR decline in patients with CKD may help identify individuals who would benefit from proactive management to minimize the risk of adverse outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT04034992.

Prevention of Chronic Kidney Disease and Its Complications in Older Adults

In an era marked by a global demographic shift towards an aging society, there is a heightened prevalence of chronic kidney disease (CKD) among older adults. The burden of CKD spans from kidney-related complications to impacting psychological well-being, giving rise to depressive symptoms and caregiver burnout. This article delves into CKD prevention strategies within the context of aging, contributing to the discourse by exploring its multifaceted aspects. The prevention of CKD in the older adults necessitates a comprehensive approach. Primary prevention is centered on the modification of risk factors, acknowledging the intricate interplay of various comorbidities. Secondary prevention focuses on early CKD identification. Tertiary prevention aims to address factors contributing to CKD progression and complications, emphasizing the importance of timely interventions. This comprehensive strategy aims to enhance the quality of life for individuals affected by CKD, decelerating the deterioration of functional status. By addressing CKD at multiple levels, this approach seeks to effectively and compassionately care for the aging population.

Deterioration of Kidney Function Is Affected by Central Arterial Stiffness in Late Life

Cardiovascular diseases affect kidney function. The aim of this study was to investigate the possible associations between hemodynamic parameters and change in kidney function in individuals aged 75 years and older. Data on hemodynamics and blood and urine samples were collected at baseline and during one-year visits. Hemodynamics were split into two groups based on median values. Changes in the estimated glomerular filtration rate (eGFR) were investigated between low and high groups for each hemodynamic parameter using analysis of variance. Changes in the albumin-creatinine ratio (ACR) were examined as binary outcomes (large increase vs. stable) using logistic regression. The population consisted of 252 participants. Participants in the high central systolic blood pressure (cSBP) group had a greater decline in eGFR than participants in the low cSBP group (-6.3% vs. -2.7%, p = 0.006). Participants in the high aortic pulse wave velocity (aPWV) group had a greater decline in eGFR than those in the low aPWV group (-6.8% vs. -2.5%, p = 0.001). Other hemodynamic parameters were not associated with eGFR changes. Hemodynamics were not associated with changes in the ACR; aPWV and cSBP appear to be predictors for eGFR decline in older age; monitoring and treatment of elevated stiffness might be helpful in order to prevent kidney function decline.

Determinants of diabetic nephropathy among adult diabetic patients on follow-up at public hospitals in Addis Ababa, Ethiopia: A case-control study

Background

Diabetic nephropathy is defined as patients with diabetes mellitus who have persistent proteinuria for at least three consecutive measurements per year, a high blood creatinine level (>130 mol/l), or a decrease in glomerular filtration rate (<60 ml/min). Limited studies were done in Ethiopia on determinants of diabetic nephropathy among diabetic patients. Therefore, this study aimed to identify determinants of nephropathy among adult diabetic patients on follow-up at public hospitals in Addis Ababa, Ethiopia, 2022.

Methods

A hospital-based unmatched case-control study design was conducted from 6 September to 9 November 2022, among diabetic patients on follow-up at public health hospitals in Addis Ababa. Using consecutive sampling techniques, a total of 442 (353 controls and 89 cases) were recruited, with a control-to-case ratio of 4:1. The data were collected using a structured and interview-administered questionnaire and variables like high-density lipoprotein, low-density lipoprotein, Glycated hemoglobin, and type of diabetes were extracted from the medical records of the patients using a checklist. The collected data were entered into Epidata 3.1 and analyzed by STATA version 15.0. Variables with a p-value < 0.25 in the bivariable logistic regression were selected for the final model. In multivariable logistic regression model fitting, variables with a p-value < 0.05 with 95% CI adjusted odds ratio have declared statistically significant risk factors of diabetic nephropathy.

Results

In this study, out of 442 study participants, 334 controls and 89 cases were included in the analysis, with a response rate of 94.6% and 100%, respectively. The majority of the study participants were 92.13% of cases and 84.13% of controls; 7.87% of cases, and 15.87% of controls were type 2 diabetes mellitus. Age 65 and above years old (AOR: 2.42; 95% CI: 1.28, 4.57); Smoking cigarette (AOR: 2.22; 95% CI: 1.18, 4.16); Non-adherent to diet (AOR: 2.11; 95% CI: 1.15, 3.84); Drinking alcohols (AOR: 1.95; 95% CI: 1.07, 3.52); Duration with diabetes more than 10 years (AOR: 3.39; 95% CI: 1.76, 6.54); Poor glycemic control (AOR: 2.19; 95% CI: 1.23, 4.28); and Low-density lipoprotein (AOR: 2.97; 95% CI: 1.69, 5.28) were found to be statistically significant risk factors of nephropathy among diabetic patients.

Conclusion

This study found that old age, smoking cigarettes, non-adherence to diet, duration of diabetes, alcohol drinking, Glycated hemoglobin A1C, and high low-density lipoprotein were risk factors for nephropathy. Hence, continuous health education on lifestyle modifications and diabetic-related complications in each follow-up visit via front-line health professionals are very essential to avert the problem.

Auditory robustness and resilience in the aging auditory system of the desert locust

After overexposure to loud music, we experience a decrease in our ability to hear (robustness), which usually recovers (resilience). Here, we exploited the amenable auditory system of the desert locust, Schistocerca gregaria, to measure how robustness and resilience depend on age. We found that gene expression changes are dominated by age as opposed to noise exposure. We measured sound-evoked nerve activity for young and aged locusts directly, after 24 hours and 48 hours after noise exposure. We found that both young and aged locusts recovered their auditory nerve function over 48 hours. We also measured the sound-evoked transduction current in individual auditory neurons, and although the transduction current magnitude recovered in the young locusts after noise exposure, it failed to recover in the aged locusts. A plastic mechanism compensates for the decreased transduction current in aged locusts. We suggest key genes upregulated in young noise-exposed locusts that mediate robustness to noise exposure and find potential candidates responsible for compensatory mechanisms in the auditory neurons of aged noise-exposed locusts.

Differences in the epidemiology, management and outcomes of kidney disease in men and women

Improved understanding of differences in kidney disease epidemiology, management and outcomes in men and women could help nephrologists to better meet the needs of their patients from a sex- and gender-specific perspective. Evidence of sex differences in the risk and outcomes of acute kidney injury is mixed and dependent on aetiology. Women have a higher prevalence of chronic kidney disease (CKD) stages 3-5 than men, whereas men have a higher prevalence of albuminuria and hence CKD stages 1-2. Men show a faster decline in kidney function, progress more frequently to kidney failure and have higher mortality and risk of cardiovascular disease than women. However, the protective effect of female sex is reduced with CKD progression. Women are less likely than men to be aware of, screened for and diagnosed with CKD, started on antiproteinuric medication and referred to nephrologist care. They also consistently report a poorer health-related quality of life and a higher symptom burden than men. Women experience greater barriers than men to access the waiting list for kidney transplantation, particularly with respect to older age and obesity. However, women also have longer survival than men after transplantation, which may partly explain the comparable prevalence of transplantation between the sexes.

Changes in renal function over time in outpatients with eGFR ≥ 30 mL/min/1.73 m2: implication for timing of renal function testing before contrast-enhanced CT imaging

PURPOSE

To evaluate the associations between comorbidities and kidney function decline at 6-month and 1-year follow-up in outpatients with initial estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m2.

MATERIALS AND METHODS

Outpatients aged 18 and older with confirmed diagnosis, who had eGFR ≥ 30 mL/min/1.73 m2 measured between April 2017 and March 2019, were included in this retrospective observational study. Of them, 30,595 included outpatients had 6-month eGFR test and 27,698 included outpatients had 1-year eGFR test. The outpatients were further divided into two groups based on initial eGFR: between 30 and 59 and ≥ 60 mL/min/1.73 m2. Impaired renal function was defined as eGFR declined to below 30 mL/min/1.73 m2. The comorbidities with P values less than 0.1 identified in univariable logistic regression models were entered into the multivariable analysis with backward selection, thereby identifying comorbidities that increased the risk of eGFR decline at 6-month and 1-year follow-up.

RESULTS

Outpatients with initial eGFR between 30 and 59 mL/min/1.73 m2 were 175.94 times more likely to have eGFR decline at 6 months, and were 94.10 times more likely to have eGFR decline at 1 year, compared with their corresponding initial eGFR ≥ 60 counterparts. Multivariable logistic regression analyses disclosed that chronic kidney disease, hypertension, and heart failure were independent risk factors for eGFR decline in outpatients with initial eGFR between 30 and 59 mL/min/1.73 m2.

CONCLUSIONS

Outpatients with initial eGFR ≥ 60 mL/min/1.73 m2 might not need routine eGFR test prior to contrast-enhanced CT scan for 1 year. In addition, chronic kidney disease, hypertension, and heart failure increased the risk of declined renal function, particularly, in outpatients with initial eGFR between 30 and 59 mL/min/1.73 m2.

Trends in renal function in Northern Sweden 1986-2014: data from the seven cross-sectional surveys within the Northern Sweden MONICA study

OBJECTIVE

The prevalence of chronic kidney disease (CKD) is increasing globally, and CKD is closely related to cardiovascular disease (CVD). CKD and CVD share several risk factors (RF), such as diabetes, hypertension, obesity and smoking, and the prevalence of these RF has changed during the last decades, and we aimed to study the effect on renal function over time.

DESIGN

Repeated cross-sectional population-based studies.

SETTING

The two Northern counties (Norr- and Västerbotten) in Sweden.

PARTICIPANTS

Within the MONitoring Trends and Determinants of CArdiovascular Disease (MONICA) study, seven surveys were performed between 1986 and 2014, including participants aged 25-64 years (n=10 185).

INTERVENTIONS

None.

MEASURES

Information on anthropometry, blood pressure and cardiovascular risk factors was collected. Creatinine and cystatin C were analysed in stored blood samples and the estimated glomerular filtration rate (eGFR) calculated using the creatinine-based Lund-Malmö revised and Chronic Kidney Disease Epidemiology Collaboration (eGFRcrea) equations as well as the cystatin C-based Caucasian, Asian, Paediatric and Adult cohort (CAPA) equation (eGFRcysC). Renal function over time was analysed using univariable and multivariable linear regression models.

RESULTS

Renal function, both eGFRcrea and eGFRcysC, decreased over time (both p<0.001) and differed between counties and sexes. In a multivariable analysis, study year remained inversely associated with both eGFRcrea and eGFRcysC (both p<0.001) after adjustment for classical cardiovascular RF.

CONCLUSION

Renal function has deteriorated in Northern Sweden between 1986 and 2014.

High Dietary Phosphorus Is Associated with Increased Breast Cancer Risk in a U.S. Cohort of Middle-Aged Women

Research has shown that high amounts of dietary phosphorus that are twice the amount of the U.S. dietary reference intake of 700 mg for adults are associated with all-cause mortality, phosphate toxicity, and tumorigenesis. The present nested case-control study measured the relative risk of self-reported breast cancer associated with dietary phosphate intake over 10 annual visits in a cohort of middle-aged U.S. women from the Study of Women's Health Across the Nation. Analyzing data from food frequency questionnaires, the highest level of daily dietary phosphorus intake, >1800 mg of phosphorus, was approximately equivalent to the dietary phosphorus levels in menus promoted by the United States Department of Agriculture. After adjusting for participants' energy intake, this level of dietary phosphorus was associated with a 2.3-fold increased risk of breast cancer incidence compared to the reference dietary phosphorus level of 800 to 1000 mg, which is based on recommendations from the U.S. National Kidney Foundation, (RR: 2.30, 95% CI: 0.94-5.61, p = 0.07). Despite the lack of statistical significance, likely due to the small sample size of the cohort, the present nested case-control study's clinically significant effect size, dose-response, temporality, specificity, biological plausibility, consistency, coherence, and analogy with other research findings meet the criteria for inferred causality in observational studies, warranting further investigations. Furthermore, these findings suggest that a low-phosphate diet should be tested on patients with breast cancer.

Kidney and Cardiovascular Effects of Canagliflozin According to Age and Sex: A Post Hoc Analysis of the CREDENCE Randomized Clinical Trial

RATIONALE & OBJECTIVE

It is unclear whether the effect of canagliflozin on adverse kidney and cardiovascular events in those with diabetic kidney disease varies by age and sex. We assessed the effects of canagliflozin among age group categories and between sexes in the Canagliflozin and Renal Endpoints in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) study.

STUDY DESIGN

Secondary analysis of a randomized controlled trial.

SETTING & PARTICIPANTS

Participants in the CREDENCE trial.

INTERVENTION

Participants were randomly assigned to receive canagliflozin 100mg/d or placebo.

OUTCOMES

Primary composite outcome of kidney failure, doubling of serum creatinine concentration, or death due to kidney or cardiovascular disease. Prespecified secondary and safety outcomes were also analyzed. Outcomes were evaluated by age at baseline (<60, 60-69, and≥70 years) and sex in the intention-to-treat population using Cox regression models.

RESULTS

The mean age of the cohort was 63.0±9.2 years, and 34% were female. Older age and female sex were independently associated with a lower risk of the composite of adverse kidney outcomes. There was no evidence that the effect of canagliflozin on the primary outcome (a composite of kidney failure, a doubling of serum creatinine concentration, or death from kidney or cardiovascular causes) differed between age groups (HRs, 0.67 [95% CI, 0.52-0.87], 0.63 [0.48-0.82], and 0.89 [0.61-1.29] for ages<60, 60-69, and≥70 years, respectively; P=0.3for interaction) or sexes (HRs, 0.71 [95% CI, 0.54-0.95] and 0.69 [0.56-0.84] in women and men, respectively; P=0.8for interaction). No differences in safety outcomes by age group or sex were observed.

LIMITATIONS

This was a post hoc analysis with multiple comparisons.

CONCLUSIONS

Canagliflozin consistently reduced the relative risk of kidney events in people with diabetic kidney disease in both sexes and across age subgroups. As a result of greater background risk, the absolute reduction in adverse kidney outcomes was greater in younger participants.

FUNDING

This post hoc analysis of the CREDENCE trial was not funded. The CREDENCE study was sponsored by Janssen Research and Development and was conducted collaboratively by the sponsor, an academic-led steering committee, and an academic research organization, George Clinical.

TRIAL REGISTRATION

The original CREDENCE trial was registered at ClinicalTrials.gov with study number NCT02065791.

Rethinking Chronic Kidney Disease in the Aging Population

The process of aging population will inevitably increase age-related comorbidities including chronic kidney disease (CKD). In light of this demographic transition, the lack of an age-adjusted CKD classification may enormously increase the number of new diagnoses of CKD in old subjects with an indolent decline in kidney function. Overdiagnosis of CKD will inevitably lead to important clinical consequences and pronounced negative effects on the health-related quality of life of these patients. Based on these data, an appropriate workup for the diagnosis of CKD is critical in reducing the burden of CKD worldwide. Optimal management of CKD should be based on prevention and reduction of risk factors associated with kidney injury. Once the diagnosis of CKD has been made, an appropriate staging of kidney disease and timely prescriptions of promising nephroprotective drugs (e.g., RAAS, SGLT-2 inhibitors, finerenone) appear crucial to slow down the progression toward end-stage kidney disease (ESKD). The management of elderly, comorbid and frail patients also opens new questions on the appropriate renal replacement therapy for this subset of the population. The non-dialytic management of CKD in old subjects with short life expectancy features as a valid option in patient-centered care programs. Considering the multiple implications of CKD for global public health, this review examines the prevalence, diagnosis and principles of treatment of kidney disease in the aging population.

Sex Differences in Age-Related Loss of Kidney Function

BACKGROUND

CKD is more prevalent in women, but more men receive kidney replacement therapy for kidney failure. This apparent contradiction is not well understood.

METHODS

We investigated sex differences in the loss of kidney function and whether any sex disparities could be explained by comorbidity or CKD risk factors. In the Renal Iohexol Clearance Survey (RENIS) in northern Europe, we recruited 1837 persons (53% women, aged 50-62 years) representative of the general population and without self-reported diabetes, CKD, or cardiovascular disease. Participants' GFR was measured by plasma iohexol clearance in 2007-2009 (n=1627), 2013-2015 (n=1324), and 2018-2020 (n=1384). At each study visit, healthy persons were defined as having no major chronic diseases or risk factors for CKD. We used generalized additive mixed models to assess age- and sex-specific GFR decline rates.

RESULTS

Women had a lower GFR than men at baseline (mean [SD], 90.0 [14.0] versus 98.0 [13.7] ml/min per 1.73 m2; P<0.001). The mean GFR change rate was -0.96 (95% confidence interval [CI], -0.88 to -1.04) ml/min per 1.73 m2 per year in women and -1.20 (95% confidence interval [CI], -1.12 to -1.28) in men. Although the relationship between age and GFR was very close to linear in women, it was curvilinear in men, with steeper GFR slopes at older ages (nonlinear effect; P<0.001). Healthy persons had a slower GFR decline, but health status did not explain the sex difference in the GFR decline.

CONCLUSION

Among middle-aged and elderly individuals in the general population, decline in the mean GFR in women was slower than in men, independent of health status.

The multispeciality approach to the management of localised kidney cancer

Historically, kidney cancer was approached in a siloed single-speciality way, with urological surgeons managing the localised stages of the disease and medical oncologists caring for patients if metastases developed. However, improvements in the management of localised kidney cancer have occurred rapidly over the past two decades with greater understanding of the disease biology, diagnostic options, and innovations in curative treatments. These developments are favourable for patients but provide a substantially more complex landscape for patients and clinicians to navigate, with associated challenging decisions about who to treat, how, and when. As such, the skill sets needed to manage the various aspects of the disease and guide patients appropriately outstrips the capabilities of one particular specialist, and the evolution of a multispeciality approach to the management of kidney cancer is now essential. In this Review, we summarise the current best multispeciality practice for the management of localised kidney cancer and the areas in need of further research and development.

Spatially Resolved Transcriptomes of Mammalian Kidneys Illustrate the Molecular Complexity and Interactions of Functional Nephron Segments

Available transcriptomes of the mammalian kidney provide limited information on the spatial interplay between different functional nephron structures due to the required dissociation of tissue with traditional transcriptome-based methodologies. A deeper understanding of the complexity of functional nephron structures requires a non-dissociative transcriptomics approach, such as spatial transcriptomics sequencing (ST-seq). We hypothesize that the application of ST-seq in normal mammalian kidneys will give transcriptomic insights within and across species of physiology at the functional structure level and cellular communication at the cell level. Here, we applied ST-seq in six mice and four human kidneys that were histologically absent of any overt pathology. We defined the location of specific nephron structures in the captured ST-seq datasets using three lines of evidence: pathologist's annotation, marker gene expression, and integration with public single-cell and/or single-nucleus RNA-sequencing datasets. We compared the mouse and human cortical kidney regions. In the human ST-seq datasets, we further investigated the cellular communication within glomeruli and regions of proximal tubules-peritubular capillaries by screening for co-expression of ligand-receptor gene pairs. Gene expression signatures of distinct nephron structures and microvascular regions were spatially resolved within the mouse and human ST-seq datasets. We identified 7,370 differentially expressed genes (p adj < 0.05) distinguishing species, suggesting changes in energy production and metabolism in mouse cortical regions relative to human kidneys. Hundreds of potential ligand-receptor interactions were identified within glomeruli and regions of proximal tubules-peritubular capillaries, including known and novel interactions relevant to kidney physiology. Our application of ST-seq to normal human and murine kidneys confirms current knowledge and localization of transcripts within the kidney. Furthermore, the generated ST-seq datasets provide a valuable resource for the kidney community that can be used to inform future research into this complex organ.

Nomogram to predict rapid kidney function decline in population at risk of cardiovascular disease

BACKGROUND

To develop a reliable model to predict rapid kidney function decline (RKFD) among population at risk of cardiovascular disease.

METHODS

In this retrospective study, key monitoring residents including the elderly, and patients with hypertension or diabetes of China National Basic Public Health Service who underwent community annual physical examinations from January 2015 to December 2020 were included. Healthy records were extracted from regional chronic disease management platform. RKFD was defined as the reduction of estimated glomerular filtration rate (eGFR) ≥ 40% during follow-up period. The entire cohort were randomly assigned to a development cohort and a validation cohort in a 2:1 ratio. Cox regression analysis was used to identify the independent predictors. A nomogram was established based on the development cohort. The concordance index (C-index) and calibration plots were calculated. Decision curve analysis was applied to evaluate the clinical utility.

RESULTS

A total of 8455 subjects were included. During the median follow-up period of 3.72 years, the incidence of RKFD was 11.96% (n = 1011), 11.98% (n = 676) and 11.92% (n = 335) in the entire cohort, development cohort and validation cohort, respectively. Age, eGFR, hemoglobin, systolic blood pressure, and diabetes were identified as predictors for RKFD. Good discriminating performance was observed in both the development (C-index, 0.73) and the validation (C-index, 0.71) cohorts, and the AUCs for predicting 5-years RKFD was 0.763 and 0.740 in the development and the validation cohort, respectively. Decision curve analysis further confirmed the clinical utility of the nomogram.

CONCLUSIONS

Our nomogram based on five readily accessible variables (age, eGFR, hemoglobin, systolic blood pressure, and diabetes) is a useful tool to identify high risk patients for RKFD among population at risk of cardiovascular disease in primary care. Whereas, further external validations are needed before clinical generalization.

Associations of kidney tests at medical facilities and health checkups with incidence of end-stage kidney disease: a retrospective cohort study

No study has assessed the association between no health checkup and end-stage kidney disease (ESKD). This retrospective cohort study, including 69,147 adults aged ≥ 40 years in Japan who were insured by the National Health Insurance and the Late-Stage Medical Care System for the Elderly, assessed the associations of kidney tests at medical facilities and health checkups with incident ESKD. The main exposure was the histories of kidney tests using dipstick urinalysis and/or serum creatinine measurement at medical facilities and checkups in the past year: “checkups,” “no kidney test (without checkup),” and “kidney tests (without checkup)” groups. During the median observational period of 5.0 years, ESKD was observed in 246 (0.8%) men and 124 (0.3%) women. The “no kidney test” group was associated with ESKD in men (adjusted subhazard ratio of “no kidney test” vs. “checkups”: 1.66 [95% confidence interval, 1.04–2.65], but not in women. Age-specific subgroup analyses identified the “no kidney test” group as a high-risk population of ESKD in elderly men (1.30 [0.70–2.41] and 2.72 [1.39–5.33] in men aged 40–74 and ≥ 75 years, respectively). Elderly men with no kidney test at medical facilities and no health checkup were at higher risk of ESKD.

Cystatin C kidney functional reserve: a simple method to predict outcome in chronic kidney disease

BACKGROUND

Kidney Functional Reserve (KFR), the only clinical kidney stress test, is not routinely measured because complexity of measurement has limited clinical application. We investigated the utility of plasma cystatin C (CysC) after oral protein loading to determine KFR in stage 3 and 4 CKD.

METHODS

Following a 24 hour low protein diet, KFR was measured after oral protein by hourly plasma CysC and compared with simultaneous creatinine clearance (CrCl) and radionuclide Tc-99m-DTPA (mGFR) measurement in an observational, single-centre cohort study of adults with CKD 3 and CKD 4. Subjects were followed for three years for fast (F) or slow (S) CKD progression, dialysis requirement or death or a combination of major adverse kidney events (MAKE-F or -S).

RESULT

CysC, CrCl and Tc-99m DPTA mGFR measurements of KFR in 19 CKD 3 and 21 CKD 4 patients yielded good agreement. KFR was not correlated with baseline kidney function. Eight CKD 3 (42%) and 11 CKD 4 (52%) subjects reached their lowest serum CysC concentration four hours after protein loading. CysC KFR and baseline serum creatinine (sCr) predicted (death or dialysis) or MAKE-F with respective AUC = 0.73 (95% CI: 0.48 to 0.89) and 0.71 (95% CI: 0.51 to 0.84). Including CysC KFR, age, baseline sCr and nadir CysC predicted a decrease in sCr-eGFR greater than 1.2 mL/min per year (MAKE-S) with AUC = 0.89.

CONCLUSIONS

Serial CysC avoided timed urine collection and radionuclide exposure and yielded equivalent estimates of KFR. Serial CysC may facilitate monitoring of KFR in clinical practice.

Distribution of estimated glomerular filtration rate and determinants of its age dependent loss in a German population-based study

Glomerular filtration rate (GFR) declines with age by approx. 1 ml/min/m2 per year beginning in the third decade of life. At 70 years of age > 40 ml/min/m2 of GFR will be lost. Thus, factors affecting loss of GFR have significant public health implications. Furthermore, the definition of chronic kidney disease based on GFR may not be appropriate for the elderly. We analyzed factors affecting absolute and relative change of eGFR over a 5 year period in 12,381 participants of the Gutenberg Health Study. We estimated GFR at baseline and after 5 years of follow-up by two different equations. Association with the decline of estimated GFR (eGFR) was assessed by multivariable regression analysis. We confirmed a median loss of eGFR per year of approx. 1 ml/min/m2. Aside from albuminuria systolic blood pressure was most strongly associated with faster decline of eGFR followed by echocardiographic evidence of left ventricular diastolic dysfunction and reduced ejection fraction. White blood cell count showed a moderate association with eGFR loss. Diastolic blood pressure, serum uric acid and serum albumin were associated with slower GFR decline in multivariable analysis. Sensitivity analysis with exclusion of individuals taking diuretics, antihypertensive, antidiabetic, or lipid lowering drugs confirmed these associations.